Limited use components for an electrochemical device

ABSTRACT

The present invention provides an ozone generating system that combines single-use elements or segments with an extended use fixture that is used to activate the single-use elements. One embodiment of the invention consists of a strip of proton exchange membrane (PEM) having the ozone producing catalyst applied directly onto one side of membrane. Optionally, the application of this catalyst may be divided into segments or patches, wherein each segment represents the limited-use portion of the ozone generator. Each segment may be advanced into a fixture that provides the balance of the electrochemical system required for operation of the ozone generator. This balance of system may include additional subsystems, with a power supply, water source, electrical contacts, electronic controllers, sensors and feedback components, being typical examples.

REFERENCE TO PRIOR APPLICATIONS

[0001] This application is a divisional of U.S. patent application Ser.No. 10/079,722 filed on Feb. 19, 2002, which is a continuation of U.S.patent application No. 09/598,067, filed Jun. 20, 2000.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The invention relates to methods and apparatus for avoidingproblems associated with extended use of electrochemical devices, namelydegradation that can occur as a result of cycling the electrochemicaldevice on and off.

[0004] 2. Background of the Related Art

[0005] Ozone has long been recognized as a useful chemical commodityvalued particularly for its outstanding oxidative activity. Because ofthis activity, it finds wide application in disinfection processes andthe removal of cyanides, phenols, iron, manganese, and detergents. Thus,ozone has widespread application in many diverse activities, and its usewould undoubtedly expand if its cost of production could be reduced.Furthermore, the relatively short half-life of ozone makes it difficultto distribute so it is generally produced on-site and usually very nearthe point of use. However, the cost of generating equipment, and poorenergy efficiency of production has deterred its use in manyapplications and in many locations.

[0006] Because ozone has a very short life in the gaseous form, and aneven shorter life when dissolved in water, it is preferably generated inclose proximity to where the ozone will be consumed. Traditionally it isgenerated at a rate that is substantially equal to the rate ofconsumption since conventional generation systems do not lend themselvesto ozone storage. Ozone may be stored as a compressed gas, but whengenerated using corona systems the pressure of the output gas stream isessentially at atmospheric pressure. Therefore, additional hardware forcompression of the gas is required, which in itself reduces the ozoneconcentration through thermal degradation. Ozone may also be dissolvedin liquids such as water but this process generally requires additionalequipment to introduce the ozone gas into the liquid, and at atmosphericpressure and ambient temperature only a small amount of ozone may bedissolved in water.

[0007] Because so many of the present applications for ozone only havethe need for relatively small amounts of ozone, it is generally not costeffective to use conventional ozone generation systems such as coronadischarge. Furthermore, since many applications require the ozone to bedelivered under pressure or dissolved in water, as for disinfection,sterilization, treatment of contaminants, etc., the additional supportequipment required to compress and/or dissolve the ozone into the waterstream further increases system cost.

[0008] Electrochemical cells in which a chemical reaction is forced byadded electrical energy are called electrolytic cells. Central to theoperation of any cell is the occurrence of oxidation and reductionreactions that produce or consume electrons. These reactions take paceat electrode/solution interfaces, where the electrodes must be goodelectronic conductors. In operation, a cell is connected to an externalload or to an external voltage source, and electrons transfer electriccharge between the anode and the cathode through the external circuit.To complete the electric circuit through the cell, an additionalmechanism must exist for internal charge transfer. Internal chargetransfer is provided by one or more electrolytes, which support chargetransfer by ionic conduction. Electrolytes must be poor electronicconductors to prevent internal short-circuiting of the cell.

[0009] The simplest electrochemical cell consists of at least twoelectrodes and one or more electrolytes. The electrode at which theelectron producing oxidation reaction occurs is the anode. The electrodeat which an electron consuming reduction reaction occurs is called thecathode. The direction of the electron flow in the external circuit isalways from anode to cathode.

[0010] Unfortunately, electrochemical ozone generators, especially thosehaving lead dioxide as the anodic electrocatalyst, experience aperformance degradation that gets worse with successive shutdowns of thegenerator or cell. This degradation manifests itself as an increasingvoltage requirement of the cell. In some applications, this degradationcan be avoided by providing a battery backup system that maintains atrickle current to the cell. In U.S. Pat. No. 5,529,683, Critz teachesthat this problem can also be avoid by applying a reverse potential tothe cell during shutdown. While these approaches to the problem may besufficient in some applications, they both presume a continuing supplyof electrical current.

[0011] Therefore, there is a need for an ozone generator system thatoperates efficiently on standard AC or DC electricity and water todeliver a reliable stream of ozone gas that is generated under pressurefor direct use by the application. It would be desirable if the systemwas self-contained, self-controlled and required very littlemaintenance. It would be further desirable if the system had a minimumnumber of wearing components, a minimal control system, and becompatible with low voltage power sources such as solar cell arrays,vehicle electrical systems, or battery power. Finally, it would bedesirable if the electrochemical cell were designed to overcome thecycling limitations inherent to existing electrochemical ozonegenerators without requiring the continued use of electrical current. Itwould be even more desirable if the electrochemical cell were designedto avoid or reduce other lifetime limiting effects, such as impurewater.

SUMARY OF THE INVENTION

[0012] The present invention provides an ozone generating system thatcombines single-use elements or segments with an extended use fixturethat is used to activate the single-use elements. One embodiment of theinvention consists of a strip of proton exchange membrane (PEM) havingthe ozone producing catalyst applied directly onto one side of membrane.Optionally, the application of this catalyst may be divided intosegments or patches, wherein each segment represents the limited-useportion of the ozone generator. Each segment may be advanced into afixture that provides the balance of the electrochemical system requiredfor operation of the ozone generator. This balance of system may includeadditional subsystems, with a power supply, water source, electricalcontacts, electronic controllers, sensors and feedback components, beingtypical examples. After an individual segment is advanced into theoperating fixture, the membrane may be hydrated by a water source andelectrical contact made to the positive (anode) face of the membranehaving the ozone generating catalyst and to the negative (cathode) sideof the membrane which may also include a catalyst layer.

[0013] After water and electrical contacts are provided to thelimited-use segment, the system now forms the basic elements of anelectrochemical cell that may be used for electrolysis. With theapplication of electrical current, the system will begin electrolyzingthe available water to generate ozone which may then be utilized. Theoperation of the generator can then continue until the performancedegrades to unacceptable levels or until the source of ozone is nolonger required. At that time the electrical power may be shut off orthe electrical contacts physically removed from the limited-use element.When the limited-use element has reached or neared its operatinglifetime, the used segment may be removed from the fixture and a newsegment advanced into position. In this manner, the process can continuewith the limited lifetime components of the electrolyzer beingcompletely replaced in a simple and potentially automated manner.

[0014] The concept of the limited-use element may be extended to includeall the elements necessary for operation of the ozone generator thatundergo degradation or consumption. While not intended to be anexhaustive list, these degradable or consumable elements may include theanodic catalyst, cathodic catalyst, membrane, performance indicators,water supply, and electrical supply. It may also be advantageous toinclude aspects of the product handling system as limited-use elements,such as including a hydrophobic, gas permeable membrane over the anodeso that ozone gas may pass directly into a process stream withoutintroducing other fluids into the cell.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] So that the above recited features and advantages of the presentinvention can be understood in detail, a more particular description ofthe invention, briefly summarized above, may be had by reference to theembodiments thereof, which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

[0016]FIG. 1 is a schematic diagram of an ozone generation system havingcomponents that are considered extended-use as well as components thatare considered limited-use and possibly disposable.

[0017]FIG. 2 is a schematic diagram of an alternate embodiment of FIG. 1having the anode catalyst formed on the anode electrical contact.

[0018]FIGS. 3a and 3 b are side and top view schematic diagrams of anelectrochemical ozone generator utilizing the disposable segments.

[0019]FIG. 4 is a detailed schematic diagram of a disposable segmentcomposed of three sub-elements such as ozone concentration indicator andelectrolyzer water source.

[0020]FIG. 5 is a cross section of the electrolytic ozone generatorhaving a vertical orientation and a flooded electrolyzer region.

[0021]FIG. 6 is a schematic of a mechanism supplying the catalyst andmembrane from separate feeds and laminated at the time of use.

[0022]FIG. 7 is a schematic diagram of a membrane and catalyst feedmechanism that removes a protective layer from the catalyst surfacebefore use.

[0023]FIG. 8 is a schematic diagram of a membrane and catalyst feedmechanism that removes the catalyst from a carrier strip and transfersthem to the membrane before use.

[0024]FIG. 9 is a schematic diagram of a membrane and catalyst feedmechanism that removes a protective layer from the segments before use.

[0025]FIG. 10 is a schematic of a membrane and catalyst strip systemthat includes a hydrophobic member over each active segment.

[0026]FIG. 11 is a simplified schematic diagram of a system makingelectrical contact to the active region with rollers rather than withplates.

[0027]FIG. 12 is a schematic side view of a filter press type stack ofelectrochemical cells for use with multiple arrays of segments.

DETAILED DESCRIPTION OF THE INVENTION

[0028] In one embodiment of the invention, the anode catalyst (such aslead dioxide) is deposited or painted onto a first side of a protonexchange membrane (PEM), either continuously or in individual segments.This proton exchange membrane is preferably in the form of a strip thatmay be coiled to form a compact roll of disposable catalyst/PEMelements. These elements may be advanced into a clamp structure orfixture having an anode contact formed from a suitable material such asporous titanium and a cathode contact formed from a suitable materialsuch as porous stainless steel or stainless steel felt. Either theelements or the clamping structure may also include an elastomer or beadand groove seal that prevents water provided to the active portion ofthe PEM strip from migrating to the unused portions of the strip whereit would have undesirable effects on the unused catalysts. When a newlimited-use segment is advanced into this clamp area, it may be hydratedby any means such as immersing in water or by placing water onto themembrane or contacts.

[0029] In a similar embodiment, the sealing portion of the elements orclamping structure may be replaced by a system of pinch rollers and/orwiper to prevent the migration of water from the active segment to theunused segment. Additionally, pinch rollers may be used between theactive segment and the used segments to ‘wring’ dry the membrane andcatalyst as it leaves to recover as much water for electrolysis aspossible.

[0030] In another embodiment of the invention, a carrier strip is formedfrom a suitable material, possibly a hydrophobic material that will notwick water from the active segment to the unused segments. This carrierstrip may be divided into segments with each segment representing alimited-use element. Within these elements a suitable membrane may besecured, whether the membrane is to be coated or otherwise placed intocontact with the appropriate catalyst(s) on the anode and/or cathodeduring operation of the cell. In a manner similar to the previousembodiment, these segments are advanced and used in an extended-usefixture, but this embodiment has the advantage that the water used forthe reaction is confined to the active segment.

[0031] In a related embodiment, to ensure that the unused catalysts andmembrane remain dehydrated before use, each segment of the carrier stripdescribed previously may have a border of sufficient width that aprotective and sealing film or cover may be stretched across the activeportion of the segment and glued, thermally welded, or otherwise adheredto the border around the perimeter. With a protective film placed oneach side of the segment, i.e., over the exposed portions of the activearea, and the film sealed around the perimeter on each side, eachsegment is then completely sealed from the environment. Prior to use,these protective films may be peeled back to expose a fresh andcompletely dehydrated segment that may then be placed into service. Inan extreme application, the entire strip or coil of unused segments maybe placed in the process water because the film will protect the unusedsegments until they are exposed for use.

[0032] Many of the foregoing embodiments are directed at keeping themembrane and/or catalyst dry, because the PEM is an ion exchange polymerin the protonated or acid form. The present invention also includesstoring electrochemical cells, whether single cells or stacks of cells,in the sodium, potassium or lithium salt form. If a membrane in the saltform becomes wet during storage, the resulting pH will be sufficientlyneutral to prevent damage to the catalyst. On a practical basis, storageof cells in the salt form is limited to storage prior to the first useof the cell.

[0033] In another embodiment of the invention, the individual segmentsof the limited-use strip may also include a suitable indicator toindicate when the desired concentration of ozone is reached or to detecta threshold concentration. An example of such an indicator is indigo dyethat is known to be bleached and loose its color when exposed to ozone.Color developing indicators are also well known which darken in color asthey are exposed to ozone. In this embodiment, either of theseindicators could be used in combination with an optical monitor builtinto the fixture. This optical monitor would then quantify, measure ordetermine the ozone concentration or whether suitable engagement hasoccurred. Alternatively, the ozone indicator could be mixed with theanode water rather than being provided separately. An importantrequirement of the indicator medium would be that it does not place asignificant demand on the ozone being generated.

[0034] In yet another related embodiment, the indicating system may bespatially separated from the electrolyzer active area so that it is incontact with the process water rather than with the anode water. In thisembodiment, the indicator would be fixed to a surface (possibly atransparent film) [Where?] and the ozone concentration of the processwater quantified by the single-use color-changing indicator.

[0035] In another embodiment of the ozone monitor aspect of thisinvention, the ozone monitor may be an electrical measurement with atypical example being oxidation-reduction potential (ORP) measurement.Since these measurements are subject to drift and may requirecalibration, it may be desirable to package limited-use or single-useprobes along with other elements on the PEM or carrier strip. This wouldallow a new set of probes to be used for each cycle thereby minimizingthe need for calibration or cleaning of the probes. A separate set ofelectrical contacts would be provided on the clamping mechanism toprovide electronic communication with a controller.

[0036] In accordance with the present invention, the source of the waterfor electrolysis may be delivered to the electrolyzer in any number ofways, including but not limited to pumping from a reservoir, dipping thecatalyst into to the water, dripping water onto the catalyst or frits,or wicking the water to the electrolyzer. As another example of waterdelivery, the system may be mounted vertically with the unused spool ofcatalyst above the water level of a water reservoir and the usedportions of the catalyst simply discharged into the water reservoir. Asingle set of pinch rollers may then be used to prevent water fromwicking out of the water reservoir to the feed spool containing unusedsegments.

[0037] In another embodiment of this invention the water used for theelectrochemical reaction may be packaged with the limited-use segments,but in a separate containment device so that the membrane and catalystremain dry until use. As an example of this embodiment, a small andsealed packet of water would be placed near the active region of theelectrolyzer segment and this packet of water pierced or ruptured whenthe anode and cathode electrical contacts clamp onto the membrane andcatalyst. The water in this reservoir will then hydrate the necessaryportions of the electrolyzer cell and continue to provide water forelectrolysis. As this water is consumed, additional water may be drawnfrom the prepackaged reservoir until the reservoir is empty. In thismanner, each individual limited-use segment of the electrochemical cellprovides all consumable materials other than electrical energy. Toextend this single-use packaging concept to its extreme, a battery maybe included to provide the power necessary for the operation of theelectrolyzer. In this embodiment, there may be no other consumable itemsother than those provided with each single-use or limited-use segmentand the remaining functions of the fixture would be limited toactivating the cell, advancing the segments, and managing the producedozone.

[0038] It may be desirable to have the catalyst and membrane totallyseparated during the storage period and only brought into direct contactimmediately before activation of the electrolyzer. Therefore, in anotherembodiment of the invention the catalyst may be deposited to a screen orscrim material that will not degrade the catalyst even if the catalystand support is moist or wet. Segments of the catalyst may then be formedon a strip of the support screen and this supported catalyst forming thebasis of the limited-use device. In this embodiment either the supportedcatalyst alone may be advanced or the catalyst and a PEM may be both beadvanced through the extended-use fixture. Since the catalyst andmembrane are separate, they each may be advanced at an individual ratedepending upon their lifetime. The PEM, for example, may be advancedwhen the cell voltage becomes excessive and the catalyst may be advancedwhen the ozone output degrades below an acceptable level. As anextension of this embodiment, it should be recognized that the physicalseparation of the catalyst and membrane inherently results in anextended lifetime since the catalyst is removed from the acidicenvironment of the membrane. Therefore, in a system where physicalseparation of the catalyst and membrane occur, limited-use may in factconsist of hundreds or thousands of cycles before any degradation of theozone production is observed.

[0039] In a related embodiment, the catalyst may be formed and stored ona separate strip or backing designed for easy release of the catalystand transfer to another surface. By this design, the catalyst may betransferred from the storage backing and applied to the PEM immediatelybefore use. Depending upon the design of the system, the catalyst may bepeeled from the PEM after use and discarded or the PEM may be advancedto a fresh area and a new catalyst patch applied. As with the lastembodiment, this embodiment has the distinct advantage that the catalystroll can get wet as long as the wet support or backing does not resultin degradation of the catalyst as would be observed in an acid systemsuch as the proton exchange membrane.

[0040] In yet another related embodiment, it may be more desirable tocut segments of supported catalysts from a feed roller completely ratherthan the above method of transfer from a backing to the membrane or ofseparately feeding a strip of supported catalyst segments. In thisembodiment, a continuous roll of supported catalyst may be cut intosegments and applied to either the PEM or to the anode contactimmediately before the electrical contacts are clamped to thePEM/catalyst segment. This system has the advantage in that it allowsthe spatial separation between the wet area and the dry storage area tobe increased since the cut segments may be transported from one regionto another.

[0041] In another embodiment, the anode catalyst is deposited to theanode contact or frit material and extended lifetime of the electricalozone generator is achieved through the physical removal of the catalystfrom the acidic membrane during periods of storage or nonuse. Since theozone producing catalyst and the membrane are not in contact, the systemwill not suffer from shelf life problems inherent to existing ozoneproducing catalysts in contact with the acidic membrane. In thisembodiment, the membrane may be packed wet and with sufficient water toprovide electrolysis for continued use or water for electrolysis may beprovided from another source. The key feature of this embodiment is thatthe extended-use mechanism is used to separate the anode from the protonexchange membrane whenever electrical power is not being delivered tothe electrolyzer system. The mechanism that brings the anode, PEM, andcathode into contact may be driven by a solenoid or other automateddevice as well as driven manually by the user. Regardless of theactuating mechanism, the anode, membrane, cathode combination may befully assembled or engaged only during use and while the system ispowered and then either automatically or manually disassembled ordisengaged when the system is turned off or power is removed. In thismanner, the performance of the lead dioxide as a catalyst for ozoneevolution will not be degraded by the PEM during periods of nonuse or oflow current density settings.

[0042] In any of these embodiments, the electrical contacts for theanode and/or cathode may be directly printed, laminated, or otherwisemade a part of the limited-use member rather than, or in combinationwith, the extended-use member. In this embodiment the contacts to theanode and cathode may extend away from the active region or the contactsmay both be placed the same side of the electrolyzer. This embodimentmay have advantages in material selection, for example, as it isdesirable to minimize the number of components exposed to the ozone gasdue to corrosion.

[0043] In another embodiment of this invention, a hydrophobic film maybe placed across the gas generating portions of the ozone generator toprevent the water used for electrolysis from leaving the anode region.More specifically, in a system where the ozone gas is to be engaged in awater or liquid process stream the hydrophobic member will act toprevent the high-quality anode water from mixing with the lower qualityprocess water. Furthermore, in an application where the process water isto be used for consumption and therefore any possibility of leadcontamination must be considered, the hydrophobic membrane may achievethe physical separation of the lead containing anode catalyst from theprocess water. Therefore, in this embodiment the limited-use segment mayconsist of a hydrophobic strip carrier with PEM segments and a catalystin contact with the PEM with an electrical lead extending out of theactive region while maintaining a tight seal between the hydrophobicstrip carrier and the PEM. A method of water delivery or release willprovide sufficient water to the electrolyzer so that the system canoperate for the desired period of time. Finally, the entire segment iscovered with a hydrophobic membrane so the anode water is confined tothe immediate region surrounding the anode. With this design, the entiresegment may be immersed or exposed to the process water.

[0044] In another embodiment, the cathode is provided with a source ofair and includes a gas diffusion layer that allows the protons to formwater rather than hydrogen, thereby reducing the potential of theelectrolyzer as well as eliminating the hydrogen gas stream.

[0045] In another embodiment, the cathode is provided with a catalyst orconsumable materials designed to convert, adsorb, react with, orotherwise eliminate the hydrogen gas stream that would otherwise begenerated during the period of time that the ozone generator isoperating.

[0046] In certain applications it may be desirable to operate the ozonegenerator on water that is not of high quality, e.g., tap water. Underthese operating conditions, ions in the water supply will reduce theconductivity of the membrane resulting in an increased potential dropacross the membrane leading to reduced efficiency and lower net ozoneproduction. Therefore, in another embodiment of the invention, aperiodic replacement of the membrane will allow the tap water fed ozonegenerator to perform at optimum efficiency simply by advancing themembrane. In this embodiment, the limited-use portion of the ozonegenerator may be the proton exchange membrane only, the catalyst only,or both elements depending upon which failure mechanism is expected tolimit the performance of the ozone generator.

[0047]FIG. 1 is a schematic diagram of an electrochemical cell, whichmight be an electrolyzer such as an ozone generation system, havingcomponents that are considered extended-use as well as components thatare considered limited-use and possibly disposable. The basic elementsof a proton exchange membrane (PEM) based electrolyzer are shown by theanode electrical contact 102, the cathode electrical contact 103, theanode catalyst 105, cathode catalyst 106, and a proton exchange membrane104. The electrochemical cell is attached to and powered by an externalpower source such as a battery or power supply 107. Of these components,the membrane 104 and catalysts 105, 106 are considered to be limited-usewhile the contacts 102,103 and power supply 107 are considered to beextended-use. The catalyst is shown coated onto a strip of membrane suchthat the catalyst forms segments of active membrane that may beindividually used as a portion of the electrochemical cell orelectrolyzer system. Furthermore, the anode and cathode electricalcontacts may be separated from the catalyst and PEM allowing thelimited-use catalyst coated PEM to be repositioned, moved or advancedindependently of or relative to the extended-use electrolyzer hardwarethat constitute the balance of components needed to form the cell.

[0048] During operation of the electrochemical cell the anode andcathode electrical contacts 102, 103 are placed or clamped in intimatecontact with the anode and cathode catalysts respectively, water isprovided to the PEM, and a voltage applied by the power supply 107.While the anode and cathode contacts 102, 103, are clamped to thecatalysts and membrane 104, a seal 108 such as an elastomer o-ringdisposed on the anode and cathode contacts is used to prevent migrationof water from the segment having catalysts 105, 106 to the unusedsegment having catalysts 105 a, 106 a and the remainder of the unusedsegments.

[0049] After use of the electrochemical cell, the anode contact alone orin combination with the cathode contact may be withdrawn, unclamped ordisengaged from the active catalyst/PEM/catalyst segment or assembly. Inthis disengaged position, the catalyst/PEM/catalyst segment may beadvanced such that an unused catalyst/PEM/catalyst segment is positionedfor use. The contacts are then clamped or pressed against the unusedcatalysts and the generator is placed back into operation.

[0050]FIG. 2 is a schematic diagram of an alternate embodiment of thepresent invention, in which the anode catalyst 205 is formed onto orremains in contact with the anode electrical contact 202 so that boththe catalyst 205 and the contacts 202,203 are considered to beextended-use components as is the power source 206. In this figure, theanode catalyst 205 is removed or disengaged from contact with the protonexchange membrane 204 during periods when the electrochemical cell, herean ozone generator, is turned off. The physical removal of the anodecatalyst away from contact with the PEM eliminates or significantlyreduces the damage to the anode catalyst (e.g., lead dioxide for ozoneproduction) that can occur when electrical power is removed from a cellwhere the catalyst remains in contact with the acidic membrane. In thisfigure, the cathode catalyst is shown to be the face of the cathodeelectrical contact rather than a distinct separate catalyst layer. Thisis most easily accomplished by utilizing the catalytic activity ofcommon metals that may also be used for electrical contact, one suchexample being stainless steel.

[0051]FIGS. 3a and 3 b are schematic side and top views of a system thatutilizes limited-use elements, such as those shown schematically inFIGS. 1 and 2. In FIGS. 3a and 3 b, the prepared membrane 303 is shownin a reel-to-reel process that is being fed from a supply or take-offspool 301, being utilized by the extended-use subsystem 311, after whichit is coiled onto a take-up spool 302. During use of the active portionof the membrane 310, clamps, solenoids, push button, actuator, or othermeans or mechanisms 308 for providing motion are used to make and breakcontact between the membrane 303 and the anode contact 313 and cathodecontact 314 shown in FIG. 1 as 102 and 103. The clamping mechanism willtypically include a guide member to maintain alignment duringdisengagement or regain alignment upon reengagement of theelectrochemical cell. These guide members may take any form known in theart, but may simply include mounting the electrode contacts 313,314 toaligned tracks or to a spring-loaded hinge resembling a clothespin.While the guide member deals with aligning the components of the cell,there must also be a way to actuate or bias the electrode contactsbetween an engaged position and a disengaged position. These actuatorsmay include automated means, such as with solenoids, hydraulic orpneumatic cylinders and the like, or manual means, such asfinger-actuated push buttons or triggers that are spring loaded. Anexample of a push button actuator requiring one push for engagement anda second push for disengagement would be the use of a mechanism likethose in retractable ball point pens.

[0052] It is also optional to provide mechanisms for incrementallystepping or advancing the array of segments into the active area of thecell. These mechanisms may be simple or complex according to theapplication and may be operated independently or in connection with theclamping mechanism. One example of a mechanism for clamping the cell inconnection with advancing the array of segments in that used in a toycap gun. In a cap gun, a single trigger disengages a cap, advances theroll of caps to align an individual cap over an anvil, and then releasesthe biased hammer to engage the cap.

[0053] Pinch rollers 304 have been added to prevent water migration fromthe wet area near the active region 310 of the membrane 303 to theunused membrane spooled as 301. An alternate or supplemental means ofpreventing water migration may be a non-rotating device such as a wiper305 shown in this figure. Pinch rollers 312 or a second wiper typemechanism may also be placed on the used membrane to recapture as muchwater from the membrane as possible before spooling the membrane on thetake-up reel 302. A portion of the extended-use system may include ahousing 306 designed to confine and direct the gas stream and to confinethe water used to wet the membrane and the water required forelectrolysis.

[0054] The support required for an auxiliary process 309 is also shownin this figure. As examples, this auxiliary process may be used inconjunction with an electrochemical cell that is an ozone generatingelectrolyzer for the detection or quantification of ozone in the spacewithin the housing 306, indexing of the membrane 303, detection ormonitoring of the ozone in the process stream, or any other analysis ofthe membrane, catalysts, anode water, process water, gas or gas spaces,etc. In this figure, the auxiliary or supplemental process 309 is shownto have both an extended-use component, such as an optical sensor, and alimited use component, such as ozone sensitive patch.

[0055]FIG. 4 is a schematic top view of an array of limited-use segmentsformed on membrane stored in a roll. The active segment of the membrane403 is subdivided to include the active catalyst 402 and supportingprocesses or materials 405, 406. This collection of limited-usecomponents represents one segment 403, preferably having individualsub-components, elements or materials that have comparable lifetimes.One example of subsystems packaged with the membrane 402 include colorindicating or color eliminating dye patches 406 for the measurement ofozone concentration. Another example is a reservoir of water that may beused for electrolysis and to hydrate the membrane. In this example, thewater may be contained in a sealed reservoir 405 which is ruptured,pierced, or otherwise tapped to provide water for electrolysis and/orhydration of the membrane.

[0056]FIG. 4 also shows a method of preventing water wicking from theactive area to unused areas through the use of hydrophobic materials ormaterials treated to prevent the migration of water. The example shownin FIG. 4 includes a hydrophobic region 404 that is subdivided toinclude the active region of the membrane and catalyst 402 as well as asupporting subsystem 406 and a possible water storage 405. To eliminateor reduce the necessity of pinch rollers or other active methods ofwater control, the active segment may be separated from the other newand unused segments by an area of additional hydrophobic, treated, orother carrier material 411. Therefore, the system may represent asegmented strip having a carrier material, for example a hydrophobicmaterial such as Mylar, Teflon, or other suitable material or plastic,that contains many segments each of which is subdivided or may containsubunits. This strip may then be handled on a reel-to-reel process asshown in FIG. 4 with the unused segments 409 on a take-out reel 407 andthe used segments 410 collected on a take-up spool.

[0057]FIG. 5 is a schematic diagram of an electrochemical cell, perhapsan electrolyzer such as an ozone generator, which utilizes thereel-to-reel apparatus for handling or managing the limited-usecomponents. In this figure, the unused segments are taken from thetake-out spool 502 and clamped in the anode 505 and cathode 506 contactsurfaces. These contact surfaces are moved by actuators 508 that mayinclude, but are not limited to, solenoids, hydraulic cylinders,pneumatic cylinders, springs and other biasing members. Water isprevented from wicking up to the unused segments by pinch rollers 503and wiper 504. It should be noted that an alternate design may furtherreduce the water available by the unused membrane by positioning thesupply or take-out spool 502 outside the main container 515. In thisschematic, the active area of the catalyst 507 is completely submergedunder the water level 514. Alternate embodiments may be envisionedwherein the active membrane may take various positions with the waterand be above the water level, partially submerged, or completely belowthe water level. FIG. 5 also includes a secondary process 510 havingboth a multi-use and limited-use components as well as rollers 510 andtake-up spool 511. The region 515 of the electrolyzer having thereel-to-reel mechanism may be separated from a secondary region 513 by astructure 512 providing distinct separation of the regions 513,515. Onesuch exemplary structure is a hydrophobic membrane designed to preventwater mixing from the mechanism region 515 with the headspace orpossibly ozone engagement or utilization region 513.

[0058]FIG. 6 is a schematic diagram of a system wherein the limited-usemember is composed of two or more parts that are manufactured, stored,or installed separately and then combined or placed in intimate contactprior to use. In the example shown in this figure, the proton exchangemembrane may be taken from one feed reel 602 while the catalyst is takenfrom a second feed reel 601. A scrim, screen, or other carrier suitablefor the application may support the catalyst. In the specific example ofan electrochemical ozone generator, this embodiment has the addedadvantage that the moisture content of the catalyst and of the membranedoes not cause degradation until the two are in contact. Therefore, boththe membrane and catalyst may coexist in the same region and under thesame conditions prior to their being placed in contact. In the extremecondition, this would allow both components to be fully hydrated or evensubmerged for extended periods prior to use without degradation oradverse results.

[0059]FIG. 6 shows the material from the individual take-out spools 601,602 placed in intimate contact first by the optional pinch rollers 603and ultimately by the anode and cathode contacts 604, 605. After use,the two materials may be coiled around separate take-up spools 606, 607or the laminated materials could be combined onto one spool.

[0060]FIG. 7 is a schematic diagram of a delivery system whereby thecatalyst is held on a backing material and covered with a removableprotection material. The catalyst is provided along with its backing andprotection material by a take-out spool 702 and the protection materialis removed prior to use by roller 704 and the protection strip collectedon a take-up spool 703. The catalyst and backing material 705 is thenplaced in contact with the membrane or complementary material 706 beingprovided by a second feed spool 701. The two materials are thenlaminated forming an active area 711 that is coiled around a take-upspool 708 after use. Various rollers such as pinch rollers 709, 710 areprovided to control the physical handling of the feed materials.

[0061]FIG. 8 is a schematic similar to FIG. 7 but where the catalyst isprovided with a removable backing material. In this figure the catalystand backing material are taken from a feed spool 802 and the catalystseparated from the backing material by a roller or other device 804 andthe backing material collected on a take-up spool 803. The catalystsegments 805 are transferred to the proton exchange membrane 806 and theactive segment 808 is provided to the active area between the electrodecontacts and clamping mechanism 810. Used membrane and catalyst may becollected on a take-up reel 808 as desired. In an alternate operationmethod, the system may be bi-directional wherein a specific catalystsegment may be applied to the membrane and then used for a period oftime. When the electrolyzer is cycled off, the rollers may be rotated inreverse such that the catalyst segment is replaced onto the backingmaterial so that it is separated from the proton exchange membrane. Thecatalyst may then be reused while being separated from the PEM betweeneach use. After the useful lifetime of the catalyst, a completely freshcatalyst segment may be applied to the PEM and the unusable catalyst 807and membrane accumulated on a take-up spool 808. Alternatively, the usedcatalyst segments may be removed from the membrane and disposedseparately.

[0062]FIG. 9 is a schematic diagram of a supply mechanism that peels aprotective layer from the segments, here including a catalyst and PEM.In this figure, the catalyst and PEM segments are supported by ahydrophobic carrier strip like that shown in FIG. 4. Each catalyst andPEM segment 901 is covered and sealed by a protective layer 902 that isbonded, glued, welded, or otherwise held or secured to the carrier stripsuch that a moisture tight seal is made. This seal is broken as theprotective member is removed, by rollers, knife, or other mechanism 904,from the segment prior to use in the clamping mechanism 905. In thismanner, the unused PEM will be unable to take up water from theenvironment, etc., so that the catalyst and membrane can be stored inintimate contact for extended periods before use without damage ordegradation. Used segments 906 may then be wound around a take-up spool907 or otherwise managed or disposed.

[0063]FIG. 10 is a schematic of a supply mechanism that provides a phaseseparation layer as a component in the limited-use material of thegenerator. In this figure, the segment carrier 1001 containing catalystsegments 1004 and sealed water reservoirs 1005 is covered with ahydrophobic element 1002 which may be placed either continuously overthe length of the carrier 1001 or just over the active area of eachsegment. Preferably, a removable material 1007 which is glued, thermallywelded, or otherwise bonded to the segment or more preferably to thecarrier strip 1001 forming a moisture tight or resistant seal enclosingat least the portion of the segment having the catalyst and PEM thenseals the active area segment. Prior to use, the sealing strip 1007 isremoved leaving the hydrophobic member as the exposed element over theactive segment. The internal water reservoir 1010 is then ruptured,pierced, or otherwise allowed to release its contents, such as by asharp protrusion 1013 extending from the face of the electrode contactor by pressure applied between the two electrode contacts, so that wateris taken up by the membrane and catalyst. Electrical contact is made byanode contact 1009 and cathode contact 1008. During operation of theelectrolyzer, the water used for electrolysis, which was providedentirely or in part by the included water reservoir 1005, 1010, isretained in the active segment by the hydrophobic membrane 1002 and thecarrier strip 1001. This provides a means of separating the pure anodewater from materials or water in the process region 1012 surrounding thesegments and the cell. Used segments 1011 are discarded or accumulatedby a take-up spool as in the other figures. It is also possible that thecontacts to the anode and cathode catalysts may be provided by alimited-use component and discarded with the catalyst and membrane.These contacts may be vapor deposited, painted, or otherwise formeddirectly onto the catalyst or backing materials or may be a metallicscreen that is laminated with the other members of the limited-usesegment.

[0064]FIG. 11 is a schematic diagram showing an alternative method ofelectrical contact to the active segment other than a flat clampingmechanism. In this figure the unused segments are held on supply spool1101 and transferred to a takeup spool 1103 after use. The segment andcarrier strip 1102 is placed between rollers 1105, 1106 to provideelectrical contact to the active segment. To increase the electricalcontact area, a metallic screen or other means of distributing thecurrent may be added to the active segment so that the electricalcontact of the outside roller 1106 with the segment does not limit thecross-sectional area of the active region of the catalyst. Theelectrochemical device is shown in a housing having a hydrophobic, gaspermeable membrane separator 1107 spanning across the housing to allowgenerated gases, such as ozone/oxygen gas from an ozone electrolyzer, tobe separated.

[0065] It should be recognized that the present invention may also beapplied to use with a plurality of electrochemical cells simultaneously,whether such cells are operated independently, in parallel or in series.In FIG. 12 it is shown that the invention may be used in conjunctionwith a filter-press type electrochemical cell stack 1201 by providingfor the limited-use segments 1202 to be positioned between the extendeduse components, including endplates 1203 and bipolar plate 1204.Disengagement of a plurality of electrode contacts within the stack, forexample bipolar plates and endplates, may be accomplished by usingsprings 1205 secured to adjacent bipolar plates or endplates and biasedto urge the plates towards disengaging the segments therebetween. One ormore actuators 1206 may then be used to compress the stack and overcomethe bias forces of the springs 1205 to bring the bipolar plate 1204 andendplates 1203 into contact with the segments 1202.

[0066] The present invention, set out in the foregoing descriptions andfigures, provides the advantage of extending the useful lifetime of anelectrochemical cell and electrochemical cell components by allowingindividual components or groupings of components to be replaced asnecessary without discarding other components that do not need to bereplaced. In particular, a PEM contaminated by the water source or acatalyst degraded by contact with an acidic PEM can be replaced withoutlaborious disassembly of the electrochemical device. Rather theinvention facilitates replacement of limited-use segments or otherwisereduces the degradation that can occur otherwise. Therefore, theelectrochemical devices of the present invention are assembled andoperated without the use of heavy tie bolts. In the case of ozoneelectrolyzers, acidic degradation of the lead dioxide anode catalyst iseither eliminated or managed without the use of a battery backup orapplication of a reverse potential.

[0067] The term “comprising” means that the recited elements or stepsmay be only part of the device and does not exclude additional unrecitedelements or steps.

[0068] While, the foregoing is directed to the preferred embodiment ofthe present invention, other and further embodiments of the inventionmay be devised without departing from the basic scope thereof, and thescope thereof is determined by the claims that follow.

What is claimed is:
 1. A subassembly for an electrochemical cellcomprising: a carrier strip divided into segments; an array of duplicatecomponents for forming a part of the electrochemical cell having anactive area, wherein each of the segments contain the array of duplicatecomponents, a cover sealed around each of the segments, wherein theduplicate components are completely sealed from the environment.
 2. Thesubassembly of claim 1, wherein the duplicate components are selectedfrom a proton exchange membrane, an anion exchange membrane, an anodicelectrocatalyst, a cathodic electrocatalyst, a selectively rupturablewater reservoir, an ozone indicator patch and combinations thereof. 3.The subassembly of claim 1, wherein the carrier strip is selected from acontinuous ion exchange membrane, a hydrophobic material, and a screen.4. The subassembly of claim 3, wherein the screen material is selectedfrom a metal, a plastic, or combinations thereof.
 5. The subassembly ofclaim 1, wherein the cover is sealed by means selected from adhesives orthermally welding.
 6. The subassembly of claim 1, wherein the cover ispeeled back to expose a fresh segment.
 7. The subassembly of claim 2,wherein the indicator patch is dyed with an ozone sensitive dye selectedfrom indigo dyes, color developing indicators, and combinations thereof.8. A subassembly comprising: a carrier strip divided into segments; anarray of duplicate electrocatalyst deposits upon the carrier strip,wherein the carrier strip may be peeled back to allow transfer of theelectrocatalyst to a surface.
 9. The subassembly of claim 8, wherein thesurface is an ion exchange membrane.
 10. The subassembly of claim 8,further comprising a cover sealed around each of the segments, whereinthe duplicate electrocatalyst deposits are completely sealed from theenvironment.
 11. The subassembly of claim 8, wherein the duplicateelectrocatalyst deposits are selected from an anodic electrocatalyst anda cathodic electrocatalyst.
 12. The subassembly of claim 8, wherein thecarrier strip is selected from a continuous ion exchange membrane, ahydrophobic material, and a screen.
 13. The subassembly of claim 8,wherein the screen material is selected from a metal, a plastic, orcombinations thereof.
 14. The subassembly of claim 10, wherein the coveris sealed by means selected from adhesives or thermally welding.
 15. Thesubassembly of claim 10, wherein the cover is peeled back to expose afresh segment.